Arthur Turrell

Good reporting on the current state of progress toward actualization of fusion as a safe and clean source of energy. Research efforts, some public and some private, involving both magnetic plasma confinement and inertial plasma confinement, are well covered. For some technical exactitude, I think the book should have included a few nuclear-reaction "equations": Production of tritium from lithium -- what reaction, exactly? Fusion of deuterium and tritium into helium -- what reaction, exactly? Fusion of helium-3 into larger nuclei -- this theoretical process, which I understand would not produce any neutron radiation, is not even qualitatively mentioned.… (mais)

At first blush, the idea of creating a star on Earth is absurd. Our sun, a thousand times as big as Earth, is just average size as stars go. It needs its minimal kind of mass to pack the core densely enough to reach ignition. It can burn out of control and fling gigantic flares of plasma into space without fear of hitting anything. Plus the heat and radiation might cause worry in some quarters. And yet, at least 25 private companies around the world, as well as several major nations, are working on doing just that- creating a star on Earth. It’s called fusion, and Arthur Turrell describes it with the comfort and ease of a features reporter in The Star Builders.

Fusion does not happen independently or naturally on Earth. Fission does. Our nuclear reactors are all fission. So are nuclear weapons. There is a natural nuclear reactor at the core in the center of the Earth, and even some naturally occurring reactors on the surface. They feed on volatile elements like uranium, can burn and explode, and leave impossibly dangerous waste even if none of those disasters take place.

Fusion reactors do not produce that kind of waste. They do not explode, and their radiation can easily be controlled. Mostly, once fusion gets going, it can keep producing for billions of years, like the sun does. This is attention-grabbing for two enormously big reasons: it is carbon-free energy and it delivers far more punch for the little fuel it consumes. Many times more. This has suddenly become very attractive. There were 88 fusion reactors in operation on Earth in 2020.

Operation is a technical word in this context, not meaning providing electricity to anyone. At the moment, the goal is to have one operate more than 10 nanoseconds (followed by interminable examination and repair before the next “shot”). The longest operational time on record is over six minutes, but this still far from a fusion plant feeding on its own fuel like the sun and all the other stars do.

The basic idea is to create plasma, which will keep things hot enough to continuously provide more fuel from heat and density-altered atoms. Plasma is pure energy, like lightning, or the flares snapping away from the sun’s gravity into space. Creating it on Earth is what the fusion industry is all about. Turrell says: “What fusion can buy the world is carbon-free energy on the scale that we need, and at the rate of deployment that we need, for the period of time that we need, in order to save the planet.”

There are two main ways to operate a fusion reactor: magnetic and inertial confinement. In magnetic confinement, the fuel is confined in a bottle made of a magnetic field, suspended in the air within the concrete chamber. This bottle magnetic field is confined within a much larger magnetic field. One confines the fuel and the other confines the resulting neutron spray to prevent damage to the (several feet thick) concrete housing. Giant magnets surround the reactor, and must be cooled and held at 10 degrees Kelvin – almost absolute zero. Yet inside, the nuclear fusion process runs to 100 million degrees Celsius. This, obviously, never occurs in nature. It is the design of the Tokamak reactor, invented by the Russians 60 years ago. It can run continuously.

For inertial confinement, continuous operation is a dream. A tiny, intricately designed and built target is pelted by lasers into collapsing on itself to generate the fusion reaction, plasma, and incredible heat. The whole process lasts ten billionths of a second, if everything works. That is the time that inertia keeps the plasma viable and everything in its place.

There are also other experimental ways that are being tested around the world, but these are two main ones. And the most successful to date.

It was not that long ago that John Lawson figured out the three major factors of fusion and how much weight they carried in making a Tokamak reactor work. His key discovery was that there is no constant. A combination of density, temperature and plasma is all that is needed: “A Tokamak that could reach temperatures of more than 100 million degrees Celsius (180 million Fahrenheit), densities of more than 10,000 billion particles in each cubic centimeter, and energy in the plasma that is confined for more than 100 seconds … would hit his requirements and ignite its fusion plasma,” Turrell says. That’s “all” it would take to create a star on Earth, according to Lawson. Finding the right amount for each factor has been a life’s work for thousands of scientists around the world.

The path of least resistance in terms of fuel is deuterium (heavy water) and tritium. Other elements will work too, but these two are common, easy to work with, and cheap. These two elements would provide an easy multiple of the energy put into ignition, once we understand how to do that continuously. On ignition, as plasma, they suddenly provide vast amounts of energy, and everyone’s goal is to see that happening for real, in a reactor. It has come close, and just a little more of this and a little less of that should prove it’s possible. For example, a hundred million degrees is already hotter than the sun.

It all works like the whole universe works, counting electrons and neutrons. Add or remove a neutron and a different element exists. Tritium is made when ordinary lithium takes on another neutron. This can be done (at least in theory), by wrapping a blanket of lithium around the reactor chamber, so the exploding rays bombard it (instead of the walls). This would be how the fusion reactor would feed itself.

Turrell says this swapping of star stuff is the essence of all matter, and life itself. “The death of stars is what has enabled us to exist. Mostly, humans are cleverly arranged bundles of hydrogen, carbon, oxygen, nitrogen, calcium, phosphorus, sodium, potassium and sulphur. Apart from hydrogen, these elements are mostly forged in the last, dramatic moments of a star’s life. We’re all made of dead stars, and hydrogen. Without fusion reactions, complex life, which is based on a variety of atoms, wouldn’t exist. Our relationship with stars and nuclear fusion goes deeper than even ancient Sun worshipping cultures could have suspected.”

Another of the great things about fusion is fail-safeness. Nuclear fission reactors have to be constantly monitored and calibrated. They can overheat, melt down and explode, spreading radiation around the world. Fusion reactors would simply die. In an error situation, the whole thing would shut down. They are “naturally self-limiting.” The radiation produced by neutrons can be stopped “with a sheet of paper” Turrell found. The biggest problem seems to be not destroying the concrete chamber casing by the constant battering. Turrell was told at one reactor site they were far more worried about scientists falling from great heights than by radiation from fusion. It turns out to be much less than the radiation everyone normally receives just living on Earth.

Turrell visited a number of fusion reactors around the world, interviewed the scientists, and saw how they differed in their approaches and their track records. The truth is we are still far from a commercial version. None of the current reactors could handle it; they are all for experimental purposes only. Right now, everything is about proof of concept, not production. In the race to find a solution to simply burning all the carbon the Earth has ever produced, fusion will not be available in time.

He was told there are five challenges to overcome on the way to clean, endless energy:
-Make plasma ten times hotter than the core of the sun in sufficient quantity and continuously
-Take that incredible heat and somehow make steam out of it to drive turbines
-Limit the damage from neutrons bombarding the reactor by choosing the right materials to withstand the pounding
-Breeding sufficient tritium out of lithium
and last but not least:
-Figuring out if the all this results in something that is commercially viable
Because so far, billions have been spent, decades consumed, and we remain years away from a working reactor, let alone populating the planet with them. We can’t even cost it out yet. Nonetheless, the star builders live exciting and rewarding lives, and The Star Builders reflects it well.

David Wineberg… (mais)